NDUMO GAME RESERVE SOUTH AFRICA Information sheet for the site designated to the List of Wetlands of International Importance in terms of the Convention on Wetlands of International Importance especially as Waterfowl Habitat South African Wetlands Conservation Programme Document No 24/21/3/3/3/15 (1996) Department of Environmental Affairs and Tourism Private Bag X447 PRETORIA 0001 South Africa INFORMATION SHEET - 2 - 1. COUNTRY South Africa 2. DATE OF COMPILATION Originally completed: January 1993 Revised: November 1996 3. REFERENCE NUMBER Not yet available 4. COMPILER Compiled by: Mr. R. Kyle Fisheries Research Officer PO Box 43 KwaNgwanase 3973 South Africa Tel: 27 35 5721011 Fax: 27 35 5721011 Revised by: Mr G. C. Marneweck Department of Environmental Affairs and Tourism Private Bag X447 Pretoria 0001 Tel: 27 12 3103789 Fax: 27 12 3226287 5. NAME OF WETLAND Ndumo Game Reserve 6. DATE OF RAMSAR DESIGNATION Not yet available 7. GEOGRAPHICAL CO-ORDINATES - 3 - 26o53' south and 32o16' east 8. GENERAL LOCATION The reserve is situated in the north western corner of Kwazulu-Natal, approximately 500 km, north, north-east of Durban. 9. AREA 10 117 ha 10. WETLAND TYPE Five wetland types which are either permanent, seasonal or intermittent occur in the area. These include: Permanent and intermittent rivers/streams/creeks; Permanent and intermittent freshwater lakes; Permanent, seasonal and intermittent saline/brackish lakes or marshes; Permanent, seasonal and intermittent freshwater marshes and/or pools; and Tree-dominated wetlands - riparian/gallery forest 11. ALTITUDE Minimum: approximately 18 m above sea level Maximum: approximately 170 m above sea level (reserve high point) Mean: approximately 30 m above sea level 12. OVERVIEW OF SITE Ndumo Game Reserve is situated at the junction of the Usuthu and Pongolo floodplain systems. The Pongolo River runs through the reserve (from north to south) in the east while the Usuthu river forms the northern border of the reserve and the international border with Mozambique. There are two major semi-permanent floodplain pans and many smaller ephemeral pans within the reserve. - 4 - 13. PHYSICAL FEATURES Geology and Geomorphology Most of the reserve is relatively low lying flat land, much of which is regularly inundated when the Usuthu and Pongolo Rivers flood. Geologically, the area comprises cretaceous beds overlain with alluvium and tertiary sediments, all of which are exposed in several areas. Lebombo rhyolite outcrops occur, principally in the western areas. Origins During the Pleistocene, sandy material which forms the Port Durnford beds was deposited over the nearly flat surface of Miocene rocks. This was followed by general lowering of sea levels causing the coastline to shift progressively to the east. Where the shoreline was located for any length of time through the sea level through the sea level being static, a system of longshore dunes developed. It is these dunes with their typical north-south orientation, subsequently much modified by wind action to produce the sands of recent ages, which characterise the landscape of the Maputaland plain. The sea level change also affected flow velocities of the rivers of the area causing them to deposit alluvial material at successively different levels. The alluvium now forms river terraces whilst the infilling forms the present day Pongolo floodplain. Hydrology There are three principal water sources to the reserve, namely the Pongolo and Usuthu Rivers and the streams in the south west. The flow in the Pongolo River in the south is regulated by a large dam 90 km upstream, while the Usuthu River is modified by irrigation abstraction in Swaziland. Some of the streams entering from the southwest tend to be saline at reduced flow rates. Eutrophication resulting from agriculture may also become a problem in these streams. The largest pan in terms of surface area, the Banzi pan, is currently artificially kept at high levels by means of a barrage (causeway). This was deemed necessary as severe scouring of the natural exit during a cyclone in 1983 eroded it and drained the pan. The second largest pan exhibits high salinities at times when the water level is low. It also has an artificial barrage at its downstream end. Soil type and chemistry The Ndumo hill is composed of red sands while east of it, the sandveld (situated mostly 30 m above sea level) is composed of undulating pallid sands. Lower down the slope, there is grey - 5 - compacted coarse sandy clay with a hard mottled layer at one metre depth. These two sandveld areas comprise about 1151 ha. The flats, comprising 6316 ha, consist of reddish sandy clay as does the western area (648 ha) of the reserve. Water Quality Marine cretaceous deposits underlie the Pongolo floodplain and the groundwater is saline. Lakes which receive seepage can therefore become quite saline (<500 to 5000 µS cm-1) during the dry winter season but summer floods flush them out and replenish them with low conductivity, turbid water (Heeg, Breen, Colvin, Furness and Musil 1978). The waters of the Pongolo system have recently had a reduced silt burden since the construction of the Jozini Dam upstream. The Ingwavuma River, however, enters the Pongolo River just outside the reserve and if it is in flood then there can still be a considerable silt load for short periods in the Pongolo River. The Usuthu River is affected markedly by agriculture upstream, resulting in reduced flows for most of the year. There are still occasional floods and in these instances the silt load is high. Nyamithi pan is fed principally by streams entering it from the south west. Intensive agriculture in the catchment has recently resulted in heavy silt loads following good rains. Eutrophication may soon result from the increased use of fertilizers in the Balamhlanga catchment. High salinities also occur in these streams at low flow rates due to salts leaching from the substrates. Depth, fluctuations and permanence Water areas in the "wet season" cover approximately 4047 ha (40% of the reserve) while in the "dry season" this shrinks to about 1518 ha (about 15%). The pans are all relatively shallow and siltation is a serious threat to them. In the early 1980's, Cyclone Domoina caused considerable siltation of Nyamithi pan while eroding a new outlet to Banzi pan. Surveys are currently under way to assess the rate of siltation of the principal pans by means of bathymetrical studies and taking cores. This is being carried out by the Council for Scientific and Industrial Research’s (C.S.I.R.'s) Water Technology Section of Environmentek. Tidal variations Not applicable. Catchment area - 6 - Apart from the catchments of the two main rivers, the only other significant catchment of the reserve is to the south west, in communally owned areas where increasing agriculture is a threat. The total area is 11 714 km2. Downstream area The downstream areas are in Mozambique and constitute a continuation of the Usuthu floodplain system into the Maputo River floodplain. Climate Little detailed information on the weather of Ndumo is available. The average annual rainfall has been given as 638 mm. The heaviest rains usually fall in middle to late summer with lighter falls in early summer. Summer temperatures often reach well above 40o Celsius. 14. ECOLOGICAL FEATURES Six major vegetation types occur in the reserve. The two related to the wetlands are: Riverine and floodplain vegetation Fairly large tracts of riverine and floodplain vegetation occur along the two principal rivers and the main pans. The floodplain grass Cynodon dactylon dominates on the ephemeral mudflats while trees such as Ficus sycomorus and Trichilia emetica dominate in the riparian forest areas. Six plant communities have been recognised on the floodplain and are grouped according to their relative periods of exposure and inundation (Breen, Heeg and Seaman 1993). These are: ·the Acacia xanthophloea - Dyschoriste depressa community which occurs near the outer edge of the floodplain under drier conditions; ·the Ficus sycomorus - Rauvolfia caffra forest community which grows along the levees of the Pongolo and Usuthu rivers; ·the Cynodon dactylon community which occurs in areas which are alternately regularly inundated and exposed, and is especially well developed around shallow pans subjected to periodic flooding; ·the Cyperus fastigiatus - Echinochloa pyramidalis community which occurs in marshy areas and tolerates longer periods of inundation; ·two Phragmites communities, each of which comprise distinct species. Both these communities occur in the wettest areas with Phragmites australis having a preference for flat, swampy areas, and P. mauritianus favouring river banks, inlet/outlet channels and pan margins where there is a fluctuation in water level; and - 7 - · the euhydrophyte communities which may either be permanent or seasonal. These occur within the zone of colonization of open waters. Permanent communities consist mainly of Trapa bispinosa and various Nymphaea species. They are best developed in those pans where the water level is not subject to extensive seasonal fluctuations. The seasonal communities consist mainly of Potamogeton crispus and Naja pectinata and normally occur where a reasonable depth of water is still retained in the dry season. The turions of P. crispus are extremely sensitive to desiccation and large plant standing crops develop where the pans do not dry out. Large turions are selectively grazed by waterfowl which stimulates production of small turions which are less easily grazed. The result is a stable grazing system (Rogers 1984, Rogers and Breen 1990a,b). Drainage line communities These occur along the seasonal streams, particularly in the south and west. Principal tree species in these communities include Acacia robusta, Schotia brachypetala and Spirostachys africana. Other important ecological features are the ephemeral small pans in the south west, the principal floodplain pans and the two main permanent rivers. Areas of fever tree Acacia xanthophloea forests also occur.